1. Field of the Invention
This invention relates to electronic tone synthesis and in particular is concerned with generating tones which complement preselected solo tones on an electronic musical instrument.
2. Description of the Prior Art
An electronic keyboard musical instrument, such as an electronic organ, is usually implemented with a number of tone switches for selecting the tones produced in response to actuated keyswitches. The tone switches are generally organized in groups which correspond to the tiers of keyboards each of which is composed of a linear array of keyswitches. Before starting to play such an instrument, the musician must confront the problem of selecting the combination of tone switches to be actuated for each of the keyboards. Since even a medium size instrument may contain about 10 tone switches per keyboard, the theoretical number of combinations of tone switches is 2.sup.10 -1=1023 for each keyboard. Obviously the musician has a very large theoretical number of selection choices. Certain considerations, based upon a certain unspecified degree of musical maturity, are used to greatly reduce the number of tone stop combinations that are eligible for selection. However, even the use of emperical tone selection rules still leaves a very large number of residual switch selection choices.
Organs designed primarily for the performance of popular music are sometimes given the generic name of "entertainment" organs. These instruments are generally designed to use solo type voices on the upper keyboard (called the solo keyboard) and accompaniment type voices are available on the lower and pedal keyboards. A common tonal selection employed by the musican is to imitate a small combo group by selecting a solo stop for the upper keyboard along with a "blending" tone color on the lower keyboard and a similar blending tone for the pedal keyboard.
The choice of an accompaniment tone is, of course, ideally dependent upon the choice that has been made for the solo tones. Based upon years of experience with a wide variety of musical effects, some emperical rulse have been formulated for selecting accompaniment tones which complement a given solo tone. These rules are predicated upon a classification of organ tones. Before the rather recent advent of the tone synthesizer, organ tones were catagorized into four tone families comprising flutes, diapasons, strings, and reeds. These tone families are not sharply defined and the classification of a tone is somewhat subjective. A close examination of the tone classes indicates that the classes differ primarily in the number of prominent harmonics as well as with the rate at which the harmonic strengths decrease with increasing harmonic number.
The emperical tone selection rules are usually instructions for choosing a tone from a given class if the solo tone is selected from a specified class. These are not hard firm rules, but at least they provide a certain degree of guidance to the novice at tone selection.